Disclaimer: I don't own Back to the Future.

Author's Note: Here's another update, as you can see, and I decided to upload them in pairs once more. In this, Doc and Alternate Marty say their goodbyes after the test of the time machine. I could say more, but it would be silly to tell you all about it when the intent here is that you read it. So here you go.

Chapter Fifteen

Sunday, July 17, 2016
06:00 AM PDT
Tannen Valley, California

Emmett Brown smiled at his friend, Martin David Tannen, as they were gathered at the abandoned Twin Pines Mall. It was Emmett who had insisted on doing the first time travel experiment of his new DeLorean here, and Marty had agreed, both for the reason Emmett cited – nostalgia – as well as the fact that there would be no one there at this time of day. Of course, if this experiment worked, this reality would be erased within the hour and no one would remember any of it anymore, so by that point it would be irrelevant whether anyone had seen them. Until he was absolutely sure whether the experiment would work, however, Emmett preferred to have absolute safety.

"How are you doing, Marty?" Emmett asked his friend, who looked surprisingly alert at this early hour. He'd known this Marty was different, but the fact that he was used to getting up early came as a shock to the seventy-five-year-old anyway, given the fact that he was used to Marty sleeping in until at least nine-thirty A.M. in the weekend.

"Pretty much all right, Emmett" Marty replied. For all that his alternate friend had preferred to be called Doc, Marty had never gotten the hang of it, and Emmett had eventually figured that it didn't matter all that much anyway.

"Very good" Emmett responded. "Now, I've put my clock in the DeLorean. I've got my watch right here, and it's synchronized with the clock. See?"

"Check, Emmett" Marty said.

"Okay, then all we have to do is get the DeLorean up to eighty-eight miles per hour, using the remote control system, and time travel should take place" Emmett said, smiling. "Too bad I can't use Einstein, but even if there was ever an alternate version of him in this timeline, he'd be long dead."

"I suppose I could have gone to look for another dog…" Marty speculated.

"That's all right, Marty" Emmett said. "I can test the machine fine without it, and frankly, I'm really eager to see my wife and kids again."

"I understand" Marty said, sighing. "I just wish I could come too. See the wonders of time travel. Visit the past, visit your world…"

"I've explained why it's impossible" Emmett replied. "But I will go to 1885 before I head to 1920. You were right last night Marty – I really can't risk doing this on my own. After seeing all this, I won't allow myself to underestimate Biff Tannen anymore – or at least, the 2016 version of him." He sighed. "Anyway, we should really be getting on with this."

He took the remote, and started driving the DeLorean backwards with it. He then used the remote to accelerate the car, and eventually allowed it to shoot out and drive over the parking lot at accelerating speeds. Emmett and Marty took care not to stand in the path of the time machine this time around – neither of them wanted to risk it if something went wrong. In fact, Emmett was kind of wondering what his original self had been thinking when he had instructed Marty to stand in the path of the time machine. He had done something similar when he first tested the time train… but then, he had just been so incredibly excited that it seemed natural to him to do so. He supposed that it had been the same case then. Of course, he had been forced to replicate the original experiment in his timeline, so he hadn't had a choice in the matter then.

He shook his head, shrugging all the thoughts off, and focused on the DeLorean. It was now nearing eighty-eight and let out familiar flashes of light. Emmett took a deep breath and stepped forwards just as the time machine was covered with light and a sonic boom sounded. It vanished into the future, leaving fire trails behind.

"It worked!" Emmett exclaimed joyfully. "This is exactly what happened in 1985 – and in 1894! We can traverse time again!"

"Wow" Marty muttered, staring at the place the time machine had been with open mouth. "Heavy." He stared at Emmett. "Where did it go?"

"I think what you mean is 'when did it go'," Emmett said, cheerfully. "The time machine went to 6:04 AM, so we'll catch up with it in one minute and forty-one seconds."

"Heavy" Marty repeated. He looked up at Emmett. "Can I go over for a second?"

"Just keep an eye on the time" Emmett replied. "You wouldn't want to get run over."

Marty shivered. "Right" he muttered, as he made his way over to the fire trails. They were still burning, although Marty saw the fire was slowly beginning to die out. "Does the car always leave these trails behind whenever it goes through time?" he asked, looking up at Emmett.

"Every single time" the inventor confirmed. "And you'll have to watch out around it when it comes back, too – it'll be frozen all over and exhaust steam. When I took the original DeLorean to 2015, I made some efforts to reduce that effect."

Marty nodded. "I'd offer you the chance to do the same now, but I guess you want to leave right away, right?"

"That's correct" Emmett said. "Granted, I would be willing to wait a couple more minutes, but after that, I'd really like to depart. I've got everything I need – the car, a plan, papers to check the changes to history against – and I can't stay in 2016 forever. History needs to be repaired."

"I understand" Marty replied. "I just wish there was some other way, though. I like having you around."

"I kind of liked meeting you, too" Emmett said, sighing. "This version of you, I mean. Of course, I already knew the regular you." He looked at his watch. "Great Scott! We've got ten more seconds to go!"

Marty rapidly got out of the way, and just in time, too. He had barely reached the place where Emmett was standing when triple sonic booms shattered and the time machine re-emerged. As Marty and Emmett looked at it, they saw it was indeed frozen all over. "Looks like you were right" Marty muttered, under his breath.

"Indeed" Emmett confirmed. "Let's look inside." He cautiously walked over to the DeLorean, being careful to avoid the steam it vented off. When he was certain everything was all right, he used his foot to push up the gull-wing door. Inside was his clock, still just as fine as it had been when he put it inside. One look at the difference between it and his watch told him the test had succeeded completely.

"Success" he whispered, amazed. "It works! It really works! Come on inside, I'll show you!"

Marty smirked, and walked over to the other side of the DeLorean. Emmett was just turning the time circuits on when he heard a yelp. "I told you it was frozen" he said, grinning.

"Must've forgotten" Marty replied. "Jeez, you weren't kidding!"

"What gave you the idea I was?" Emmett replied, as Marty used the same method he'd just deployed to open his door. "Look, here are the time circuits. As you can see, the Destination Time is still 6:04 AM, the Present Time is 6:05 AM, and the Last Time Departed is 6:02 AM." He shook his head. "If I get out of this all right, I might consider adding seconds to that. It gives a more precise view."

"I think this works fine" Marty said, dazed. "This is heavy. So, you can go anywhere in time with this thing?"

"Anywhere between January 1st, zero AD – or more accurately, one AD or one BC, I'm not really sure – and December 31st, 9999 AD" Emmett replied. "I never thought a widening of those limits was necessary, and for this machine, I only need a select couple of dates anyway."

"Such as March 24th 1920" Marty said.

"And September 1885 of course" Emmett replied. "I was wondering whether I should go to the sixth or the seventh, considering the state of my younger self and yours on that day and what would happen if we, for some reason, didn't return. I eventually decided to pick the seventh – your counterpart should be more slightly more aware of my situation by then, and he won't have to keep his secret about this adventure for as long."

Marty nodded. "I suppose I could give you some of those mind influencers your other self made to use on him – me to make sure he doesn't remember, but I guess you wouldn't like to use them for ethical reasons" he said.

"That's right, and I'm not sure whether it would work either" Emmett responded. "After all, once we succeed in our mission, this whole reality will be erased and so will those devices. And I can't wipe your brain with an invention that doesn't exist." He shook his head. "Anyway, time to set the destination time." He put in September 7th, 1885, 6AM. "I'd offer you a short ride, but I'm not sure what purpose that would serve."

"I wouldn't know either" Marty muttered. "Well, at least I've still got your papers. I could try to build another one of these time machines."

"You could" Emmett agreed. "But I'm not sure you could manage, and whether or not you should hire any scientists for it… who knows what they might do with the knowledge."

"Yeah, I think I've gotten the idea" Marty said, smiling. "Time travel really is something to handle responsibly, isn't it?"

"It definitely is" Emmett said. "Your father gave us the clear example what happens when this machine falls into the wrong hands – twice – and we can't afford to repeat that." He stared at Marty, as they stepped out of the DeLorean. "Well…"

"Guess that's it" Marty muttered.

"Not entirely" Emmett corrected him. "I still need to collect trash for my journey to 1885. Would you like to help me with that?"

"No need" Marty said. "I made sure the trash cans weren't cleaned last night, and there's one right over there. All you have to do is walk over and collect all the cans and banana peels you need."

"Ah, now that's convenient" Emmett said. "Thanks, Marty!" He walked over to the trash can.

"It's okay" Marty said, shrugging. "The least – and the last – I could do for a friend."

Emmett sighed, as he pushed all the trash into the Fusion generator. Such devices were more common in this alternate 2016 than they were in the real one, where they hadn't yet been invented, or at least not perfected. He supposed that some of what the Tannens had done had been for good rather than for evil… although he didn't like the way they'd deployed it.

"I'm sorry I have to leave, Marty" he whispered, staring at the ground absent-mindedly. "It was nice getting to know you and I will always treasure the time I've spent with you, despite the fact that it was in an alternate reality. But…" He sighed. "There is no other way."

Marty smiled faintly. "Well, you'll have the other me" he said. "You could always hang out with him in 1985. You may say that you like having moved to the Nineteenth Century, but…"

The forty-eight-year-old remained silent, causing Emmett to frown. "What are you implying?" he asked.

"That you might want to think about moving back, Emmett" Marty said. "I can't guess what kind of relationship you had with the other me, although I'm sure it was different from what you and I had in the past few weeks. But despite that, I can be sure of one thing – that you miss him. He was your friend, your only friend, before you met this Clara woman in the Old West, and now you're ninety years apart."

"Slightly more, even" Emmett said, sighing.

"I know" Marty said. "But it doesn't have to be that way. The future is whatever you make it, right? And if you want to move back home…"

"Clara won't agree with that" Emmett said. "She likes visiting the future, but too much of it makes her nervous. Moving to 1985 is something I can't expose her or the kids to. And Marty doesn't need me in his life. He – you – has become a successful musician. Why would he want to spend time with a childhood memory like me?"

"Because you're friends" Marty said. "You told me you saved each others lives so many times. He won't tell you because he thinks you're happy in the past and you are, but wouldn't you be much happier if you were in the same time period again? To him, it's more like he lost you anyway, after so many times when he almost did, and he knows intellectually that you're alive and well, but maybe he's not all that well… and he just won't speak up about it when you visit him."

Emmett sighed, and shook his head. "You don't know" he muttered. "You're from a completely different reality. You have no idea what is going on in our world."

"Maybe I don't have the complete picture" Marty said. "But I can guess what's happening. And you could at least try to find out what the other me thinks about it. At worst, you get a 'no', and that won't be the end of the world. Didn't you tell me that if you put your mind to it, you…"

"I know, I could accomplish anything" Emmett said, interrupting his friend. "But you just don't understand. I…" He sighed, staring at Marty. "I'll think about it, okay? That's all I can promise."

"I suppose it's got to be enough" Marty said. He hugged the man who had helped him get back on a good path, away from all the vices he'd committed in his youth, and who had been his friend. Emmett smiled at him, and ruffled Marty's hair. He did kind of miss the young boy who had always eagerly participated in his experiments, who had always been kind to him, who had rarely ever judged him, who had…

Well, never mind that right now. Emmett pulled himself loose from the embrace and entered the DeLorean, while Marty shut the gull-wing door on the other side. "Goodbye" he said.

"Goodbye" Marty replied.

The time machine slowly accelerated across the parking lot, away from Emmett's lifelong friend. It came to a halt at the other side of the lot. Emmett stared around to see the Twin Pines Mall sign once more reminding him how wrong this world was.

"Things have to change" he muttered, under his breath. "And they'll change now."

He shifted the DeLorean into gear and accelerated across the parking lot. The speed quickly passed sixty miles per hour, and Emmett could barely keep track of the way the numbers kept climbing ever swifter. He passed Marty at eighty-two, and smiled at his friend for one last time. Then, he focused on the windshield as the DeLorean hit eighty-eight miles per hour. The flux capacitor lit up, there was a familiar sparkle of electricity, and a few seconds later, the machine broke the time barrier and vanished from Tannen Valley.